Answer:
the area of the mat = total area added minus the original area of the water color painting.
length of the mat is:
L = 21 in + 3 in + 3 in because 3 in is added to each side
L = 27 inwidth of the mat is:w = 11 in + 3 in + 3 inw = 17in
Area mat = (27 in x 17 in) - ( 21 in x 27 in)
area mat = 108 sq in is the area of the mat
To find the percent you take 18 and divide it by 48, so you get 9/24 or 3/8, by using calculator you get .375 which is 37.5% then you multiply by 100 to convert a decimal to a percentage.
Seven tenths
Forty seven and nine tenths
Eighteen and eight one hundredths
One hundred twenty five and twenty three thousandths
One hundred and twenty six thousandths
One hundred fifty and seventy five thousandths